Some thoughts on a timeline of events spurred by trying to reconcile FCNY receiving substantial European aid and the EU not being able to control their Caribbean territories
2034- FCNY comes into existence because Victoria would be unable to absorb it due to its importance and massive population. Europe would be unlikely to support it at this stage because everything is going to putting out at fires at home and making sure Russia stops at Finland and Poland. Food and support probably comes from the New American Confederation.
2038-NAC collapses making FCNY very vulnerable, however the reasons Victoria didn't absorb it earlier still apply. Europe would see that FCNY is the only viable successor to the USA they have access too so supporting it would move up in priority, but there would still be very little to spare. This is probably the period were most of the treaties from Victoria limiting FCNY come from. There would still be some room on long island for agriculture, but a lot of Victoria's agricultural exports for that sweet hard currency were probably to FCNY.
2047- the pacific republic is subjugated making FCNY the most legitimate successor to many, meaning that refugees that previously wouldn't have gone to it due to it being nextdoor to Victoria(probably most of them) would now be more willing to go there, greatly boosting its population. Conveniently, this is about the time international trade starts to pick up again, so FCNY can start converting agricultural land to housing for the new population and getting less reliant on Victoria.
2050's- we know that sometime around 2060 that the EU puts the UK back together and that the EU is stable enough that it can contribute to a international economy, so the 2050s would probably be the decade that it puts itself back together. The countries that didn't collapse get reasonably stable and help put together the ones that did (eg Spain, France) or at least stabilize the situation (Italy probably). The lack of everything being on fire means a growing amount of spare budget that could be spent on FCNY, which probably increases after continental EU is stable enough that they start trying to reintegrate the Caribbean EU, where a friendly port on the other side of the Atlantic would be very helpful. Brazils outreach to the Guianas probably happens in the mid 50's as France is still disunited, but enough time has passed that the international economy has had several years of being on an upward trend of not dying, giving Brazil ehough confidence to do its own thing.
2060's- The EU starts to really be able to act on a global stage, French Guiana gets reintegrated (with autonomy) maybe some other Caribbean territories too, shenanigans in North Africa start to really get going, FCNY aid keeps flowing as it creeps ever closer to Maximum Land Use. Also trying really hard to keep the Balkans from exploding too hard.
2070s- the fact that Argentina has been getting Russian investment for over a decade and still hasn't really done anything against Brazil, and has faced no consequences for that is probably one of the things contributing to the sense that Russia's power is on the decline.
